The present invention relates to a pen, and more particularly to an air pressure measuring pen.
The conventional air pressure measuring pen, as shown in FIG. 1, includes a pen tube 1, a measuring head 2 mounted on tube 1, a piston 3 received in tube 1 also receiving therein a sealing piece 4, a spring 5 mounted bwtween piston 3 and piece 4, an indicating rod 6 capable of protruding out of tube 1 and having an outer scale 7 and an ink holder 8 therein, and a threaded fixture 9 respectively fixing rod 6 and holder 8 in tube 1 and rod 1. In use, head 2 is inserted upon an air valve of a tire, the pressurized air in the tire will protrude, through piston 3, sealing piece 4 and spring 5, rod 6 out of tube 1 to show the air pressure in the tire.
Such air pressure measuring pen must have the tube 1 large enough to receive therein rod 6 requiring to be troublesomely provided with an inner long hole to receive therein ink holder 8. In order to measure the air pressure and to write with the present pen, fixture 9 must first be unscrewed from tube 1. In addition, when rod 6 is protruded out of tube 1 by the tire air pressure, rod 6 easily gets inadvertently retracted into tube 1 to force the user to measure the air pressure anew.